The invention relates generally to microwave antennas matching networks, and more particularly to microstripline matching networks for coupling the four elements of a quadrifilar microwave antenna to respective networks within receiver, transmitter or transceiver units.
Divider-combiner networks are known which couple multiple antenna elements as multiple power elements with correspondingly circularly equal phase delays to a single load. The invention addresses particular problems of coupling a single load to four circularly polarized antenna elements which are arranged in 90 degree phase relationship. Divider-combiner networks are known to work bilaterally, in transmit and in receive modes. Hence, the present invention is disclosed as an embodiment of a signal coupler which is coupled to quadrifilar antenna elements which receive in a 90 degree phase relationship to each other and the signals of which are combined prior to be coupled into a single preselector network. It should be understood, however, that advantages disclosed herein are also applicable a reversal of the antenna function according to which a transmitter applies signals through the divider-combiner network to respective quadrifilar antenna elements to radiate the signals to a desired receiver installation.
It will become apparent that the disclosed invention relates particularly to a satellite relay mobile communications system in which a great number of mobile earth stations are expected to communicate via a single satellite relay station to an earth base station. Antennas and corresponding antenna coupling circuits of the mobile earth stations are consequently under constraint to be efficient from both functional and cost standpoints. Functional considerations which seek to minimize size and shape of mobile earth antennas are also inherently related to system cost reduction. The size of antenna assemblies for mobile transceiver units is considered a source of possible problems because of limited mounting space for such antenna assemblies on mobile equipment, such as trucks or automobiles. The operation of the mobile transceiver units presupposes an exposure of the respective antenna assemblies to the position of the satellite relay, desirably omnidirectional quality, and further, from a practical standpoint, a practical shape and size realization to permit an antenna assembly to be mounted on the roof of a truck cab, or a similar sky-accessible location of a vehicle. A compact size of a desirable antenna assembly would further reduce a wind resistance profile at the top of a moving vehicle.